Treatment of obstructive sleep apnea (OSA) for stroke prevention and recovery represents a rare chance to achieve transformative impact on post-stroke care and outcomes. OSA is highly prevalent after stroke (~75%) and is a known risk factor for poor functional outcome, mortality, and recurrent stroke. Furthermore, OSA is readily treated by a safe, simple, and relatively low-cost therapy, continuous positive airway pressure (CPAP). Observational studies have already demonstrated better stroke outcomes among patients who use CPAP, and multiple pilot trials have hinted at the benefits of CPAP after stroke. These studies have laid the foundation for a definitive trial on the role of CPAP in post-stroke management. The pressing need for this critical next step is highlighted in the latest American Stroke Association secondary stroke prevention guidelines. Therefore, the investigators now propose a phase III, open-label, blinded-endpoint assessment, multicenter, randomized, controlled trial to determine (1) whether treatment of OSA with CPAP after acute ischemic stroke or high-risk transient ischemic attack (TIA) helps to prevent recurrent stroke, acute coronary syndrome, and all-cause mortality 6 months after the event, and (2) whether treatment of OSA shortly after acute ischemic stroke improves stroke outcomes at 3 months. This study capitalizes on an efficient and cost-saving design involving a 6-month prevention trial with an embedded 3-month recovery trial. Many years of pilot work have identified the challenges related to the diagnosis and treatment of OSA after stroke. These valuable insights - combined with innovative digital and biomedical technology - have contributed to this highly pragmatic trial in which feasibility is paramount. In particular, as polysomnography and CPAP titration are seldom tolerated just after acute stroke, OSA will be identified through use of a portable cardiopulmonary sleep apnea test, and treated with an automatically adjusting CPAP device. Through state-of-the-art methods, subjects will receive centralized, real-time, nightly monitoring of CPAP use and proactive care management to maximize CPAP adherence. This approach simplifies and streamlines the diagnosis and treatment of OSA, which will facilitate implementation in hospitals with low resources. Consequently, this trial provides StrokeNet with an opportunity to use its network more fully, and will permit positive trial results to be readily translated into community settings across the U.S. This study represents a rare opportunity to change post-stroke care in a fundamental manner with a safe, cost-effective intervention that could improve both recovery and prevention in a substantial proportion of patients.